1. Field of the Invention
The present invention relates to back light module, and more specifically, to a back light module with an improved heat transfer rate.
2. Description of the Prior Art
Backlight units are known in the art. The backlight unit, which is a key element in the fabrication of liquid crystal displays, is widely used in digital cameras, PDAs, vehicle satellite navigation systems, computer monitors, flat panel TVs and so on. Typically, a backlight unit, which is generally installed underneath a display panel, comprises a light source (or multiple light sources) and a light diffusion means for providing users and consumers with diffused, ample, and comfortable backlighting. Light penetrates the overlying display panel and forms various images controlled by pixel electrodes densely arranged on the display panel. Backlight units are typically divided into two major categories: edge light type and direct-type, wherein the direct-type backlight unit can provide higher intensity of light and is thus more suited for large size display panels, such as display panels or TV panels, than the edge light type.
Please refer to FIG. 1 of a cross-sectional view of a back light module 10 according to the prior art. As shown in FIG. 1, the back light module 10 is disposed under a display panel 12 and comprises at least one light source generator 14, a diffusing plate 16 disposed between the light source generator 14 and the display panel 12, a light guide plate (LGP) 18 disposed between the light source generator 14 and the diffusing plate 16, and a reflecting sheet 20 disposed under the light source generator 14 and fixed on a housing 22. The light source generator 14 is employed to generate a light source, and the reflecting sheet 20 is employed to upwardly reflect the light source generated by the light source generator 14 and thereby increase the light use efficiency of the back light module 10. The light guide plate 18 is employed for scattering the light source to the diffusing plate 16, and the diffusing plate 16 is employed for further scattering the light source to the display panel 12. The housing disposed under the reflecting sheet 20 is utilized to assemble the diffusing plate 16, light guide plate 18, reflecting sheet 20 and light source generator 14. In addition, the diffusing plate 16 further comprises at least one prism 24 disposed on a surface of the diffusing plate 16 to reduce the difference of the luminous intensities on the display panel 12 in advance. The quantity and placing order of the prism 24 employed are defined by the specification of the back light module 10.
However, in most cases, the light source generator 14 is composed of a cold cathode fluorescent lamp (CCFL), and the cold cathode fluorescent lamps are paralleled arranged in a small chamber inside the back light module 10. As a result, the heat generated during the operation of the back light module 10 can be entirely dissipated to the air outside the back light module 10 and is therefore accumulated inside the back light module 10, leading to an abnormal high temperature of the light source generator 14, which eventually causes malfunctions and reduces the product lives of components related to the back light module 10.